Effects of different plantations on soil aggregates in the Nayman sand region

： Abstract To analyze the composition of soil aggregates and their stability changes in different plantation forests in the Nayman sand region and to select the best forest type for soil and water conservation as well as wind and sand stabilization, the soil in the understorey of poplar, oil and camphor pine plantation forests in the Nayman sand region was used as the research object, and the composition of soil aggregates in the 0 - 20 cm, 20 - 40 cm, and 40 - 60 cm soil layers was investigated using dry and wet sieving methods, and the soil stability evaluation index was used to evaluate soil condition. The results showed that: (1) the content of large agglomerates in the three plantation sites differed significantly between the dry and wet sieve results. Their PAD values further indicated that water-stable agglomerates were more representative in reflecting agglomerate stabilty in plantation forests in the Nayman sand region, and the number of large agglomerates with R >0.25 was significantly higher in the 0 - 20 cm soil layer than in the 40 - 60 cm under the two sieving conditions. (2) Combining the effects of different plantation forests on soil agglomerates MWD, GMD, D, and R >0.25 values showed the best structural properties of camphor pine soils, which had the highest water stability and relatively low D values. (3) The soil agglomerate diameter index and the fractal dimension D are clearly linearly related to the content of each grain size, but the positive and negative thresholds of the correlation coefficients differ, indicating that the 2 mm and 0.25 mm grain classes are particularly important dividing lines in the soil agglomeration process, which can be used as intuitive parameters to characterize soil mechanical and water stability, respectively. The combined experimental results indicate that the planting of camphor pine in the ecologically fragile Nayman sand area can effectively improve the soil structure and is suitable for the extension in the sand consolidation work in this area.